Okay, let's talk about this funky little bottle that somehow became my aquarium's best friend. First things first - YES, it smells like Satan's toilet. Prepare your nose or do the application outside like I did.
I've got a 55g planted tank that's been running for 2 years. Started using this during water top-offs and holy moly - within 12 hours my water went from 'meh' to crystal clear. Even knocked out some stubborn black hair algae I'd been battling forever.
Pro tip: Turn off UV lights before using (12-24hrs). Saw debris floating initially but it cleared up fast. Fish are visibly happier - colors popping, more active. My Fluval 407 filter pads stay suspiciously clean now.
The smell though...whew. Like rotten eggs had a baby with a sewage plant. But it disappears instantly once in water. Worth it for the results - I've gone months without water changes, just evaporation top-offs.
Planning to use it in my new Walstad setup too. 10/10 would recommend (with nose plugs).